Short-circuit detectors



Aug. 23, 1955 0. K. SCHWENZFEIER SHORT-CIRCUIT DETECTORS Filed Aug. 1, 1952 I N V EN TOR. 07-7-0 56f/WE/VZF67ER BY United States Patent Ofiice 2,716,216 Patented Aug. 23, 1955 SHORT-CIRCUIT DETECTORS Otto K. Schwenzfeier, McCook, Nebr.

Application August 1, 1952, Serial No. 302,279

1 Claim. (Cl. 324-133) This invention relates to a device for quickly and easily locating short-circuits in automotive vehicle systems.

The wiring systems of automotive vehicles and the like are so compact and involved that it is exceedingly diflicult to locate short-circuits or grounds caused by worn insulation and other faults.

The principal object of this invention is to provide a simple, portable and easily-used device which will enable a mechanic to quickly and easily locate short-circuits and grounds in vehicle wiring systems without dismantling or disturbing the wiring.

Other objects and advantages reside in the detail construction of the invention, which is designed for simplicity, economy, and efliciency. These will become more apparent from the following description.

In the following detailed description of the invention, reference is had to the accompanying drawing which forms a part hereof. Like numerals refer to like parts in all views of the drawing and throughout the description.

In the drawing:

Fig. l is a side view of what might be termed a short indicator and circuit energizing element as used in the invention;

Fig. 2 is a longitudinal-section, through the element of Fig. l, with the electrical circuits shown diagrammatically;

Fig. 3 is a side view of a second element of the improved short-circuit locator by means of which the exact location of the circuit defect may be accurately located;

Fig. 4 is a vertical section through the locator of Fig. 3, taken on the plane of the drawing; and

Fig. 5 is a circuit diagram illustrating the use of the improved device.

The improved short-circuit testing and locating device comprises two cooperating elements, a resistance element, as shown in Figs. 1 and 2 and a detecting element, as shown in Figs. 3 and 4.

The resistance element consists of a sutiable housing in which is mounted an audible alarm device 11, which may be of any deisred nature such as the magnetically vibrated diaphragm similar to the sound device of an automobile horn, a magnetic coil 12 having a magnetically permeable core 13 positioned to attract a resilient armature 14, and an alarm cut-off switch 15. The housing 10 is preferably provided with a screened sound emitting opening 16 positioned over the alarm device 11.

Two test conductors 17 and 18 extend from the housing 10 each terminating in any suitable attachment device, such as an alligator clip 19. The conductor 17 is connected to the armature 14 and to one terminal 20 of the coil 12. The conductor 18 is connected to the other terminal 21 of the coil 12 and the latter terminal of the coil is connected by means of a suitable conductor 24 with one terminal of the alarm device 11. A normally open contact 22 is also positioned to be closed by movement of the armature 14. The normally open contact 22 is connected by means of a conductor 23 through the switch 15 to the other terminal of the alarm device 11.

The detecting element of Fig. 3 comprises a tubular housing 25 having a removable cap 26 holding a lamp 27 and a reflector 28 in place similarly to a conventional flashlight. A lamp 29 is supported in and electrically grounded to the reflector 28 and the housing 25. The tip contact of the lamp 29 bears against the positive terminal of a conventional flashlight battery 30. The opposite terminal of the battery 30 is contacted by a spring blade 31 which supports the battery and maintains contact at the lamp 29.

The spring blade 31 is insulated from the housing 25 and the lower portion thereof extends resiliently across the housing to form an armature blade 32. A magnetically permeable ring 38 consisting of a stationary, semicircular ring section 33, a stationary bracket section 34, and an arcuate hinge section 35, is mounted on the bottom of the housing 25. The upper extremities of the ring section 33 and the bracket section 34 are mounted in a suitable insulating plug 36 in the bottom of the housing and extend upwardly through the plug in parallel, spaced relation.

The section is hinged to the section 34 upon a suitable hinge 37. The lower extremities of the sections 33 and 35 contact each other to form the complete ring 38.

A magnetically attractable bar 47 is mounted on the switch blade 32 over the parallel extremities of the sections 33 and 34 and a signal contact 48 is positioned below the blade to be contacted thereby to close a circuit through the housing 25 to the lamp 29. A finger hook 39 projects from the hinged section 35.

Operation Let us assume that the conductor 40 is grounded at some point throughout its length, as indicated in broken line at X. The operator disconnects the cable terminal 46 from the battery terminal and connects the test conductor 18 to the terminal 45 by its attachment clip 19. The other test conductor 17 is then connected to the cable terminal 46 so as to place the coil 12 in circuit with the conductor 40 and the switch 15 is closed.

The current from the battery 43 flows through the conductor 18, the coil 12, through the conductor 17 to the lead conductor 40 and thence through the conductor 40 to the ground X and back to the grounded terminal 44 of the battery. This energizes the coil 12, causing it to attract the armature 14 so as to close a circuit through the contact 22, the switch 15 and theconductor 23 to the alarm device 11 to vibrate the diaphragm therein so as to cause an audible tone to be emitted. This indicates at once that there is a ground in the selected lead conductor 40 at some point throughout its length.

The switch 15 is now thrown to the open position, which deenergizes the sound device but allows the current to continue to flow through the coil and the grounded circuit. The coil 12 places sutficient resistance in the circuit to prevent damage from the shorted ground The operator now opens the ring 38 on the detecting element of Fig. 3 and places it about the conductor 40 adjacent its terminal 46. The magnetic field surrounding the energized conductor electro-magnetically induces magnetism in the magnetically permeable ring 38. The tWO upper extremities of the magnetized ring 38 attract the bar 47 on the switch blade 32 to cause the to close the signal circuit at the contact 48 to allow current from ,the battery 43 to flow through the lamp 29 lighting the latter. The ring 38 is now moved along the conductor 40 and the lamp will remain lighted until the testing device has been moved beyond the position of the ground X. Since there is no current flowing in the conductor 40 beyond this point, due to the accidental ground X, no magnetism will be induced in the testing ring, and the switch blade 32 will be released to open the contact 48 and the lamp 29 will be deenergized. The operator is thereby definitely informed as to the exact point in a shorted circuit where the damaging ground or short occurs by the extinguishement of this test lamp 29.

- The testing ring 38 can be opened to pass obstructions along the conductors by manipulation of the finger grip 39 to open the ring until the obstruction is passed.

It can be seen from the above that very circuit or group of circuits'in an automotive electric system can be first tested by the audible signal device to determine the individual circuit in which the ground or short occurs. The indicated circuit can then be tested along its length by the detecting element to exactly locate the shorted point.

The ring 38, when closed at its bottom, forms a horseshoe-type magnet, the lines of magnetic force being concentrated at the spaced upper extremitiesfor eflicient attraction of the bar 47 and blade 32. The ring may be formed from soft iron or any other material which is I easily and efficiently permeable to magnetism.

The coil 12 has been referred to as magnetic, due to the necessity of attracting the armature 14. The principal function of the coil 12, however, is to provide a resistance element in the shorted circuit.

While a specific form of the improvement has been described and illustrated herein, it is to be understood that the same maybe varied, within the scope of the appended claim, without departing from the spirit of the invention.

0 Having thus described the invention, what is claimed and desired secured by Letters Patent is:

A device for determining whether an electrical conductor is electrically energized, comprising: a tubular, me-

switch blade 4 tallic housing; a reflector positioned in and electrically grounded to one extremity of said housing; a lamp bulb supported in and electrically grounded to said reflector and having a tip contact extending into said housing; a

battery in said housing with its positive terminal in con-- tact with the tip contact of said bulb; a spring blade mounted in said housing in insulated relation thereto and acting against the negative terminal of said battery to urge the latter toward said bulb; an armature blade resiliently mounted at its one extremity in said housing in insulated relation thereto and in circuit with said spring blade, said armature blade extending transversely of said housing adjacent the other extremity thereof; an insulating plug closing the other extremity of said housing; a fixed, metallic, semi-circular ring section having its upper extremity embedded in and extending through said plug into said housing; a fixed metallic bracket section similarly embedded in and extending through said plug in spaced relation to the upper extremity of said ring section; an arcuate,.me-

tallic hinge section hinged upon said bracket section and positioned to swing into contact with the lower extremity of said fixed ring section to form a closed ring when desired, the upper extremities of said ring and bracket sections terminating Within said housing in spaced relation to said armature blade, so that when magnetism is in-1 duced in said closed ring, said armature blade will be attracted toward said extremities and a contact mounted in and grounded to said housing and positioned in the path of said armature blade so that when the latter is attracted, a circuit will be closed through said lamp bulb to illuminate the latter.

References Cited in the file of this patent UNITED STATES PATENTS 1,000,938 Le Pontois Aug. 15, 1911 1,015,192 Knopp Jan. 16, 1912 2,685,061 Stelzemuller July 27, 1954 FOREIGN PATENTS 121,612 Australia June 19, 1946 28,994 Great Britain June 21, 1911 

